Good Water Area or Bad Water Area

Hi all
I have been losing fry at different stages and in different systems and could not work out why,
went to my test kits Ph / KH / GH / ammonia / nitrite / nitrate all seemed fine. Tested water out of the tap which tested at 7.5 which is the normal crappy welsh water, Then i tested the same water after heating it up and airating
over night as normal, when the same water was tested again it was coming out at 8.4 so that told me i was giving the fry Ph burn every time i did a water change so problem solved ( after losing some 3,000 to 4,000 fry ).

So that got me thinking why is my water Ph so high when the same water go,s to liverpool and runcorn and warrington and there Ph is around the 6.8 so that got me to thinking with all the fish keepers on this forum all around the country does any body have the same sort of problems with there water companies, And do you get the PH changes as to
PH starting like mine at PH 7.5 and then rising to PH 8.4 after airating.
cheers Tony

Do a ph test, then very carefully put an airline into the test liquid, and blow gently into it. You should see that the pH drops as you blow, now taking care not to spash the liquid everywhere, connect the airline to an air pump, and watch in amazement as the pH rises again!....

The more carbon dioxide (CO2) in the water, the lower the pH will be, vigourous airation drives off the CO2. Conversely, your breath contains higher levels of CO2 which as it disolves in the water causes the pH to fall. If you start at a pH of 7.0 and drive 90% of the CO2 from the water your pH will rise to 8.0.

It's certainly a good idea to aireate water before adding it to your tanks, but try aireating more gently, but for longer; or let the water stand for a while to reestablish a more natural CO2 level.

Also, big water changes are more likely to cause big swings in the pH of the aquarium water, that's one of the reasons why I usually limit myself to 10 to 20% changes.